1. Field of the Invention
The present invention generally relates to ferroelectric storage media, and more specifically, a ferroelectric storage medium including a thin surface layer having the characteristic that charge migration is much more rapid than the charge migration characteristic of the underlying ferroelectric layer.
2. Description of the Related Art
Storage density of all magnetic disk storage devices is currently increasing at a very high rate superior even to Moore's Law. Application strategies assume this continued growth. For example, the current “computing on demand” business strategies will require very large storage databases. At the opposite end of the scale, the continued development of hand held devices requires the availability of increasingly high density miniaturized storage systems.
Despite strategies based on the ever-increasing availability of higher density storage, the technical reality may be that magnetic disk storage technology is approaching limitations to further scaling improvement.
Magnetic disk storage density has been increasing faster than Moore's law, at an approximate factor of double per year, but scaling of magnetic storage engineering is showing signs of breakdown. Introduction of new techniques such as AFC (Antiferromagnetic Compensation layers) has been required to maintain scaling up to now, and further projected increases in storage density rely on the new technique of perpendicular recording.
However, perpendicular recording is a complex technology which has not yet been demonstrated successfully at the required high densities. It is questionable whether magnetic disk technology can be relied upon to increase storage density beyond approximately 100-200 Gb in−2 (Gigabitsper square inch).
Replacing magnetic storage media on the disk with ferroelectric media has the potential for much higher densities, since ferroelectric bits are on the scale of one nanometer. But, while magnetic dipoles cannot be depolarized by the nonexistent magnetic monopoles, the ferroelectric dipole can be. Without loss of its bulk polarization state, the surface change can be depolarized even by stray electric charges, posing serious problems for ferroelectric disk technology. So far, no solution to this surface depolarization problem is known for ferroelectric disk technology.